Immigrationists like you, John Micklethwait and Mark Leonard are living on another planet. You know little about the UK, and understand even less, and you despise its people. You’re just a bunch of mad scientists who want to turn this world into some PC identikit-funky-multi-culti-melting pot.
The UK is streets ahead of many countries in welcoming immigrants from around the world and we have more to teach other countries in that regard than we do to learn from them. What would you rather be? A Briton of Japanese descent or a Japanese of British descent? Exactly.
If you want immigration to ‘enrich’ and ‘reinvigorate’ a country, I suggest you look to New Zealand, which is dour, prim, and far more provincial than Australia, or even the UK. Forget fusion food and R&B, it might give them a few more attractive women.